Dolby Pro Logic IIz: Taking a second listen

The "height speakers" of Dolby Pro Logic IIz didn't make much of an impression on us, so we gave the setup another audition.

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CNET listening room
The CNET New York listening room, set up for the Dolby Pro Logic IIz. Sarah Tew/CNET

Recently, Steve Guttenberg, our resident audio guru, took a listen to the first AV receiver to offer Dolby Pro Logic IIz. And he wasn't impressed.

Pro Logic IIz is the latest surround format from Dolby Labs. This one utilizes "height speakers" placed above the left and right front-channel speakers. The configuration Guttenberg tested utilized a 7.1 configuration (a standard 5.1 setup, plus 2 height speakers), but Pro Logic IIz is designed to support 9.1 as well (7.1 plus 2). That will presumably be supported in future

According to Dolby's Web site, the advantages of Pro Logic IIz are as follows:

With Dolby Pro Logic IIz, rain in a movie now seems to be actually falling on the listener's roof, concert videos bring a more intense sense of being at the performance, and orchestral works deliver more palpable depth, power, and connection.

In games, the added dimension increases the realism and immerses players more deeply than ever in the action.

Because it processes only nondirectional sounds for the height channels, Dolby Pro Logic IIz maintains the integrity of the source mix and the effects are always appropriate to the material. The added dimension complements the sound from the rear-surround speakers, adding spaciousness while honoring the original intent of the content creator.

Alas, Guttenberg could barely hear a difference when Dolby Pro Logic IIz was engaged: "The height speakers didn't make a discernible difference. I couldn't hear them at all, so I increased the height speaker volume by 3 decibels. Still no difference."

Needless to say, Dolby and Onkyo (the maker of the TX-SR607, which is the first IIz-compatible hardware) weren't too happy with that evaluation. So, we told them we'd give it a second chance, with more ears in the room.

For Round Two, Steve Guttenberg (again), Executive Editor David Carnoy, Senior Associate Editor Matthew Moskovciak, and I crowded into the CNET audio room. Dolby suggested specific scenes in "Ratatouille" and "The Two Towers," and we also had "Blade Runner" on hand. As before, we were listening to the Onkyo TX-SR607 fed by a standard Blu-ray player, using the excellent Aperion Intimus 4T Hybrid SD surround sound speaker system, plus two extra Aperion 4B surround speakers providing the "height" effects. (The height speakers are shown on the high stands on the photo above; the black speakers sitting directly on top of the cherry Aperion towers are those of the Samsung HT-AS730, which was not powered up during this evaluation.)

All of the demo scenes involved rainy weather. We tried each one with Dolby Pro Logic IIz engaged, then again with standard Dolby Digital. Each time, it was nearly impossible for us to discern a difference between when the height speakers were engaged (IIz) or when they weren't (standard). Then we cranked up the volume on the height speakers to maximum--still hard to detect them. We also tried the height speakers on their sides, to see if a change in dispersion pattern would matter. Finally, we disconnected the lower front left/right speakers, so only the height speakers (and the center channel dialogue speaker) were emitting sound. It was only at that point that we could determine that they were actually engaged from a remote listening position (previously, we had put our ear up to them to confirm that they were powered up).

Put simply, our second round of tests effectively duplicated the first, but this time with three additional people in the room experiencing the same underwhelming results.

A big part of the problem is the mental expectations that come with seeing those height speakers looming over the home theater. There's a discernible placebo effect--your mind wants to hear something coming from them. Indeed, we frequently thought we were hearing sound from the high speakers, only to find out that we were still in standard Dolby Digital mode--the upper speakers weren't even engaged.

That's problem number two: when properly mixed, surround soundtracks are amazingly enveloping. And the fact is that all three of those movies have excellent, state-of-the-art mixes. They sound amazing in 5.1 as is; going from 5.1 to standard 7.1 (rear surrounds) or "height" 7.1 may add a hair's breadth of ambiance, but it's not going to be nearly as impactful as the jump from 2.0 stereo to 5.1 surround.

What's it all mean? Here's our takeaway:

>> You're not missing anything by not upgrading your home theater to Dolby Pro Logic IIz, at least in its current iteration.

>> You shouldn't avoid buying receivers that support Dolby Pro Logic IIz. It's going to be a standard feature in many mid- to high-end receivers hitting in 2009, so you're not really paying extra for IIz. While the IIz experience fell flat, the Onkyo TX-SR607 otherwise offers excellent audio performance and an impressive feature package, especially considering its $500 price.

>> Later iterations of Dolby Pro Logic IIz may create more of an aural impact, perhaps with soundtracks that are optimized to take advantage of it.

>> Take Steve Guttenberg's earlier advice: Instead of investing in a pair of height speakers, invest that money in better front left/right speakers or--if your receiver supports dual subwoofers, such as the Onkyo--a second subwoofer instead. Those upgrades will deliver sonic improvements you won't have to strain to hear.

And that's pretty much the bottom line for me on Dolby Pro Logic IIz, at least as it's currently implemented.

Agree? Disagree? We'd love to hear what you think.